Yes, there is MUCH that is routinely not 'disclosed'. That does not necessarily add up to deception.

Old gear inherently comes with risks based on age and normal wear. Repairs are often made to improve the condition of items before sale, moreso in autos than in cameras or electronics perhaps. The acceptability of that is based primarily on appearance and functionality as much as it does on 'disclosure". A honest return/refund policy can mitigate that (except when the buyer is a lying, scum-sucking, cheat who knowingly breaks a camera and then claims it "broke in the mail"... like one experience I had here.) But when a repair was attempted in an amateurish way and is known to have not been of "resonable quality", and known damage exists (whether it affects functionality or not, and whether it is visible or not) and are knowingly not mentioned, then there are issues that can easily be interpreted as concealment and dishonesty.